FIG. 1 is a diagram to show a conventional power supply 10 for supplying power to a gate driver of a liquid crystal display (LCD) system, which includes a transistor M1 connected between a voltage source VGH and an output VGHM, a transistor M2 connected between the output VGHM and a resistor RE having an end connected to a ground terminal GND, and a controller 122 to switch the transistors M1 and M2 to generate a voltage VGHM supplied to a power input of the LCD gate driver. Typically, the transistors M1 and M2 and the controller 122 are integrated in a same package 12. FIG. 2 is a waveform diagram of the voltage VGHM of the power supply 10 shown in FIG. 1. During the period from time t1 to time t2, the transistor M1 is on and the transistor M2 is off, so that the voltage source VGH charges the output VGHM to pull up the voltage VGHM to the level VGH. During the period from time t2 to time t3, the transistor M1 is off and the transistor M2 is on, so that energy is released from the output VGHM to the ground terminal GND and thereby decreasing the voltage VGHM.
However, with the increase of the LCD panel size, the loading of the power supply 10 is getting heavier, thereby increasing the energy required for charging to and discharging from the output VGHM, while the charging and discharging period of the power supply 10 is constant or may even become shorter. Therefore, higher discharge speed is required for the power supply 10 as the LCD panel size increases. Conventionally, smaller resistor RE is used to increase the discharge speed of the power supply 10. Unfortunately, this will increase the discharge current flowing through the resistor RE and thereby cause great heat generation and power consumption.
Therefore, it is desired a solution to reduce the power consumption of such power supplies.